1. Field of the Invention
The invention relates to ground clamps; and, more particularly, to a ground clamp for use in welding workpieces which permits the workpiece to be rotated during welding.
2. Description of the Prior Art
In electric welding, a workpiece being welded must be connected to the ground conductor or cable of an electrical welding apparatus. This is accomplished by means of a ground clamp connected to both the cable and the workpiece.
Although several clamping devices have been devised and marketed in the past to permit a ground wire to be removably affixed to a pipe during the time that an electric welding operation is being performed thereon, the majority of these devices have maintained the ground wire in a fixed relationship with the pipe, with the result that as the pipe is rotated during a welding operation the ground wire become twisted and kinked. It will be apparent that such clamps are highly unsatisfactory, not only from the standpoint of damaging the ground wire due to twisting and kinking, but in diverting the welder's attention from his work to watching the ground wire to see that it is not twisted during the time the pipe is being rotated. Upon the second wire being kinked or twisted, it frequently is damaged by having one or more of the electrical conducting strands situated therein broken, with the result that the remaining strands in the cable are subjected to carrying a heavier electric load than that for which they are designed.
In most prior art devices, when the workpiece is rotated during welding, as in welding a circumferential seam in a pipe, the cable becomes wrapped around the workpiece. This wrapping makes such welding inconvenient due to the need to unwrap the cable or to move the clamp periodically.
Certain prior art devices have been suggested to avoid this problem. In U.S. Pat. No. 2,475,051 to Raymond, a ground connector is disclosed which is rigidly clamped by means of nuts to the work member. The connector is adapted to receive rounded apertured ends of a conductor, requiring an elaborate ball and spring arrangement to retain the conductive members in electrical contact.
In U.S. Pat. No. 2,642,560 to Elkens, a cable from a welding apparatus is clamped to a member rotatably mounted on the balance of a ground clamp by a ball bearing. Electrical contact occurs through the balls of the bearing.
In U.S. Pat. No. 3,058,082, an electrical connector is disclosed having a conductor connected to a connector, the electrical contact occurring from a disk rotating with the cable, to disked, resilient contact members.
It can be seen that Raymond, Elkins and Messerli are rather complicated devices of specific structure wherein electrical contact is provided through components that can easity become corroded in use or erode thus rendering such contact erratic.
There exists a need for an inexpensive ground clamp which can provide good, electrical contact between a workpiece and welding apparatus wherein the cable from the apparatus does not entangle during welding operations.